1. Field of the Invention
The invention relates to a fuel property sensor and a fuel property detection device. More specifically, the invention relates to a fuel property sensor and a fuel property detection device advantageously suitable that detects a state of a mixed fuel of a biofuel and a hydrocarbon fuel.
2. Description of Related Art
In recent years, following the increased usage of biofuels, internal combustion engines for vehicles that can use not only a biofuel but also a mixed fuel obtained by mixing a biofuel and a hydrocarbon fuel have been researched and developed. However, the state of biofuels deteriorates rather easily with time. Therefore, it is desirable that the deterioration state of biofuels be detected when the biofuel is used.
For example, Japanese Patent Application Publication No. 2009-293437 (JP-A-2009-293437) discloses a method for determining the deterioration of a biofuel. More specifically, with the method disclosed in JP-A-2009-293437, a thermometer and a kinematic viscometer are disposed in an intake pipe of an internal combustion engine and the temperature and kinematic viscosity of the biofuel are measured. According to the description of JP-A-2009-293437, the kinematic viscosity of biofuel changes according to the deterioration state thereof, and therefore by using this principle it is possible to determine the deterioration of fuel on the basis of temperature and kinematic viscosity.
The continuous use of deteriorated fuel in an internal combustion engine using a biofuel or a mixed fuel of a biofuel and a hydrocarbon fuel as an engine fuel can result, for example, in deterioration of fuel injection valves and accumulation of deposits. Therefore, it is desirable that the fuel deterioration state be detected. However, when the deterioration of fuel is determined on the basis of kinematic viscosity of the fuel, as in the technique described in JP-A-2009-293437, a kinematic viscometer and a thermometer have to be provided only for determining fuel deterioration. As a result, the cost of fuel deterioration determination is increased.